Bob Evans, Supernova Hunter

Bill Bryson knows how to tell a good story. He always loved science, and he wanted to know “Wait, how did we figure that out?” His A Short History of Nearly Everything is the story of how we figured things out. Here Bryson recounts his meeting with Bob Evans, amateur scientist extraordinaire.

By day, Evans is a kindly and now semiretired minister in the Uniting Church in Australia… But by night he is, in his unassuming way, a titan of the skies. He hunts supernovae.

Supernovae occur when a giant star, one much bigger than our own Sun, collapses and then spectacularly explodes, releasing in an instant the energy of a hundred billion suns, burning for a time brighter than all the stars in its galaxy. “It’s like a trillion hydrogen bombs going off at once,” says Evans.  [But] most are so unimaginably distant that their light reaches us as no more than the faintest twinkle.. It is these anomalous, very occasional pricks in the crowded dome of the night sky that the Reverend Evans finds.

To understand what a feat this is, imagine a standard dining room table covered in a black tablecloth and someone throwing a handful of salt across it. The scattered grains can be thought of as a galaxy. Now imagine fifteen hundred more tables like the first one — enough to fill a Wal-Mart parking lot, say, or to make a single line two miles long — each with a random array of salt across it. Now add one grain of salt to any table and let Bob Evans walk among them. At a glance he will spot it. That grain of salt is the supernova.

[When Bob asked the astronomical community] if they had any usable field charts for hunting supernovae, [they] thought he was out of his mind. At the time Evans had a ten-inch telescope — a very respectable size for amateur stargazing but hardly the sort of thing with which to do serious cosmology — and he was proposing to find one of the universe’s rarer phenomena. In the whole of astronomical history before Evans started looking in 1980, fewer than sixty supernovae had been found. (At the time I visited him, in August of 2001, he had just recorded his thirty-fourth visual discovery; a thirty-fifth followed three months later and a thirty-sixth in early 2003.)

Evans, however, had certain advantages. Most observers, like most people generally, are in the northern hemisphere, so he had a lot of sky largely to himself, especially at first. He also had speed and his uncanny memory. Large telescopes are cumbersome things, and much of their operational time is consumed with being maneuvered into position. Evans could swing his little sixteen-inch telescope around like a tail gunner in a dogfight, spending no more than a couple of seconds on any particular point in the sky. In consequence, he could observe perhaps four hundred galaxies in an evening while a large professional telescope would be lucky to do fifty or sixty.

Looking for supernovae is mostly a matter of not finding them. From 1980 to 1996 he averaged two discoveries a year—not a huge payoff for hundreds of nights of peering and peering. Once he found three in fifteen days, but another time he went three years without finding any at all.

“There’s  something  satisfying,  I  think,” Evans said, “about the idea of light traveling for millions of years through space and just at the right moment as it reaches Earth someone looks at the right bit of sky and sees it. It just seems right that an event of that magnitude should be witnessed.”

Buy A Short History of Nearly Everything.


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